Handheld devices such as mobile phones, personal digital assistants (PDAs) and other mobile devices, such as laptop computers and digital cameras, nowadays are often equipped with a small pointing device, such as a joystick, to facilitate actions such as for example menu selection, navigation, gaming and web browsing. These pointing devices are capable of outputting positional signals which represent the position of an actuator with respect to a base of the device. The output signals are, for example, used for moving a cursor on a display screen.
The actuator itself may be biased to return to a rest position when no external force is exerted on it. Ideally, when the actuator is in its rest position, the device outputs corresponding positional signals indicating the rest position. In reality the value of the positional signals in this case often represents a position close to but not entirely equal the rest position; there is always some inevitable noise in the positional signals which can cause a cursor controlled by these signals to wobble on a display. Moreover, the actuator may be somewhat misaligned when in the rest position, causing an offset in the positional signal and corresponding cursor-drift.
To solve these problems, a threshold can be applied to the positional signal output of a pointing device. The cursor movement along a direction then becomes non zero only when the corresponding positional signal is larger than a certain threshold value. In order to eliminate cursor drift and wobbling when the actuator is in its rest position, the threshold is usually set to a value larger than noise and any likely residual offset.
A drawback of this thresholding method is that it can lead to anisotropic cursor movement and reduced sensitivity of the pointing device, in particular when at least one of the positional signals is close to an associated threshold value.
It is an object of the present invention to provide a signal processing method for at least reducing undesired anisotropic cursor movement.
It is a further object of the present invention to improve the accuracy of a pointing device.